One of the major factors in present day printer mechanisms is the desire for ever increasing operating speeds. One of the accompanying disadvantages occurring in printers, especially of the impact type, is the ever increasing noise occurring during printing. For example, considering high-speed band printers of the impact type, a closed loop band having two or more sets of alphabetic and numeric characters moves in a direction transverse to the direction of feed of a paper web, and a large plurality of hammers, typically equal in number to the number of characters per line which the printer is capable of printing, are capable of being independently and selectively triggered to impact a raised character on the band against an inked ribbon and the paper web to form characters on the paper web. Obviously, the large number of hammers utilized and the extremely fast operating speeds yield a printer capable of high-speed printing operations, typically of the order of 600 lines per minute or greater, with 132 characters per line, but also having the disadvantage of creating noise which is both annoying and distracting to the equipment operators. Obviously, as the number of printers within a room increases, the noise significantly increases adding to printing capability and, unfortunately, adding to the annoyance and distraction created by the printers.
The noise generated by printer mechanisms is airborne to the user or operator. The conventional method for preventing noise from reaching the operators is to completely enclose the printer, including the means for paper handling and stacking, with a large cabinet.
The large cabinets or enclosures which are required further include doors and windows which must be made airtight to prevent the escape of undesirable noise. The doors and windows are required to permit necessary observation and to permit easy removal and replacement of paper for use by the printer. Since the smallest openings in such housings cause the noise level to increase markedly, this type of cabinet, in addition to being quite large in size, tends to be costly to manufacture, not only due to the amount of materials required, but also due to the extreme care which must be exercised to make all openings noise tight.
Such cabinets must also be lined with materials such as foam having good acoustical attenuation properties to prevent sound reverberation within the enclosure which would otherwise lead to transmission through the walls of the cabinet. To date, very little of the noise is attenuated in cabinet designs of this type, requiring airtight doors, windows and the like to keep airborne noise from escaping to the exterior of the cabinet.
It is, therefore, both a serious and important problem to be able to provide attenuating means to reduce noise to more acceptable levels while at the same time minimizing the amount of cabinetry necessary to achieve the desired results.